1. Field of the Invention
The present invention relates to a liquid crystal display (“LCD”), and more particularly, to a photo-luminescent (“PL”)-LCD having improved light utilization efficiency, pixel-to-pixel luminance uniformity and color balance.
2. Description of the Related Art
LCDs are non-emissive displays that require a separate backlight device and Red (“R”), Green (“G”) and Blue (“B”) color filters for pixels to display a color image on a screen.
The R, G and B color filters separate white light emitted from the backlight device into red, green and blue lights, respectively. The R, G and B color filters each transmit only light of a specific wavelength, resulting in significant optical loss. Thus, a high luminance backlight device is required to produce an image with sufficient luminance.
U.S. Pat. Nos. 4,822,144 and 4,830,469 disclose PL LCDs using phosphors excited by ultraviolet (“UV”) light and having higher light utilization efficiency than LCDs using color filters. The UV light used in the PL LCD is near visible UV light and is generated from UV light activated phosphors, which are different from electron beam activated phosphors used in conventional cathode-ray tubes (“CRT”).
The PL LCD should use UV light with a long wavelength, which is absorbed less in the liquid crystal. However, red phosphors among phosphors excited by UV light with a long wavelength have lower light utilization efficiency than blue and green phosphors. Accordingly, conventional PL LCDs using UV light with a long wavelength have a pixel-to-pixel luminance difference and an inferior color balance caused by the pixel-to-pixel luminance difference. Accordingly, improving the pixel-to-pixel luminance difference and the inferior color balance are desired.